This invention relates generally to medical devices, and more particularly concerns an improved guide wire configured to conduct ultrasound energy for use in the ultrasonic treatment of lesions located in hollow anatomical structures.
In typical percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient through the brachial or femoral arteries and is advanced therein until the distal tip thereof is in the ostium of the desired coronary artery. A guide wire and a dilatation catheter having a balloon on the distal end thereof are introduced through the guiding catheter with the guide wire slidably disposed within an inner lumen of the dilatation catheter. The guide wire is first advanced into the patient""s coronary vasculature until the distal end thereof crosses the lesion to be dilated and then the dilatation catheter is advanced over the previously introduced guide wire until the dilatation balloon is properly positioned across the lesion. The balloon may then be inflated to treat the lesion. Thereafter, a stent device may be located at the treated lesion, if deemed necessary.
In xe2x80x9cultrasonicxe2x80x9d angioplasty, an ultrasonic angioplasty catheter is similarly advanced over a guide wire to an area of a vascular lesion or blockage, and mechanical vibration at ultrasonic frequencies, generated typically by a piezoceramic transducer located at the proximal end of the angioplasty catheter, is delivered along an ultrasonic angioplasty transmission member or wire to a distal catheter tip. When the distal catheter tip abuts the lesion, vibration of the distal end of the ultrasonic angioplasty transmission member removes the obstruction by mechanical impact and cavitation. The guide wire that is advanced so as to cross the lesion is useful in properly aligning the catheter and assisting in its progress through the lesion as the ultrasonically-vibrating distal tip ablates the lesion.
Advancement of a guide wire to a desired location within a passageway or vessel may be difficult or impossible in cases where there exists a total or near-total blockage of the passageway or vessel. For example, in percutaneous transluminal coronary angioplasty (PTCA) procedures, the presence of a complete occlusion within the lumen of a diseased coronary artery may prevent the tip of a guide wire from being advanced through such occlusion lesion. An angioplasty catheter may likewise be prevented from being advanced to a proper operative location across the occlusive lesion. In such instances, the inability to advance the guide wire through the fully occluded coronary vessel may necessitate abandonment of the PTCA procedure and/or the election of an alternative, more invasive, procedure such as cardio-thoracic surgery. Thus, it would be highly desirable to develop a guide wire that is capable of safely boring or creating a tunnel or passageway through a total or near-total occlusion.
In ultrasonic angioplasty techniques, accurate positioning of the ultrasound transmission member in the vasculature system to be treated requires that the guide wire first be properly located across the lesion. Should the lesion be a complete blockage or a blockage so complete that the guide wire cannot be positioned across the lesion, a highly flexible ultrasonic delivery system with a low profile, especially for coronary ultrasonic angioplasty procedures, so that the catheter can more easily navigate the various vascular passages to be advanced to the occlusion is desirable. Nickel-titanium superelastic alloys have been useful in these respects as an ultrasound transmission member. Tapering or narrowing the distal end of an ultrasound transmission member to enhance flexibility of the ultrasound transmission member at its distal end is known from U.S. Pat. No. 5,304,115 (Pflueger et al.). While such tapering or narrowing typically decreases the rigidity and improves the bendability of the ultrasound transmission member, a significant increase in amplitude of the ultrasonic energy occurs at the tapered or narrowed region. Such an increase in amplitude can cause an increased likelihood of fracturing or breakage of the ultrasound transmission member at that point during use. It would be desirable to provide a guide wire having increased flexibility and amplification of ultrasonic energy, yet still be less prone to fracturing or breakage.
Hence those skilled in the art have recognized a need for an improved guide wire capable of transmitting ultrasound energy and providing improved characteristics of strength, fatigue resistance, and elasticity for an ultrasonic delivery system for use in the treatment of intravascular blockages. In particular, a need has been recognized for an improved guide wire capable of transmitting ultrasonic energy from an ultrasound generating device located outside the body to a site within the body for purposes of ablating obstructive matter. The present invention fulfills these needs and others.
Briefly, and in general terms, the present invention is directed to an improved ultrasound transmission guide wire for use in biological passageways. In one more detailed aspect, the invention is directed to an improved guide wire for use in an ultrasonic angioplasty PTCA catheter system for ablating lesions in the vascular system of a patient.
Turning now to more detailed aspects, the invention is directed to an ultrasound transmission guide wire for use in an ultrasonic angioplasty device, the ultrasound transmission guide wire having an elongated shaft, a proximal end configured to be connected to an ultrasound transducer, and a distal end for applying ultrasonic energy to an area of vascular lesion, the ultrasound transmission guide wire comprising a distal portion with at least one amplification region of reduced cross-sectional diameter, a core of ultrasonic transmission material, and an outer jacket surrounding a usable portion of the elongated shaft. In a further aspect, the ultrasound transmission guide wire comprises threads disposed at its proximal end, the threads configured to connect to a connecting device for an ultrasound transducer to thereby communicate ultrasonic energy to the elongated shaft and to the distal end of the ultrasound transmission guide wire.
In yet further more detailed aspects, the ultrasound transmission guide wire comprises a first generally cylindrical section having a first cross-sectional diameter, and a second generally cylindrical section distal to the first section and having a second cross-sectional diameter that is smaller than the first cross-sectional diameter, the amplification region being formed at a proximal portion of the second generally cylindrical section. The ultrasound transmission guide wire further comprises a plurality of generally cylindrical sections, each of the plurality of generally cylindrical sections having reduced cross-sectional diameter relative to a proximal adjacent section resulting in a plurality of amplification regions in the cylindrical sections of reduced cross-sectional diameter. The ultrasound transmission guide wire further comprises a conically tapered section interposed between the first and second cylindrical sections. In further detail, the ultrasound transmission guide wire further comprises a plurality of conically tapered sections interposed between adjacent ones of the plurality of generally cylindrical sections.
Turning to other detailed aspects, the ultrasound transmission guide wire further comprises an enlarged application portion located at the distal end of the elongated shaft, the enlarged application portion configured to apply ultrasonic energy to a biological lesion. In more detail, the enlarged application portion comprises a rounded portion having a diameter exceeding the diameter of the elongated shaft immediately proximal to the rounded portion. And yet further, the enlarged application portion comprises a smooth ball tip having a diameter exceeding the diameter of the elongated shaft immediately proximal to the ball tip.
In another detailed aspect, the outer jacket is formed of a non-metallic material. Further, the outer jacket is formed of shrink tubing. In another aspect, the outer jacket is formed of rubber, and in yet a further aspect, the outer jacket is formed of plastic.
In regard to the material of the guide wire, in one aspect, the ultrasound transmission guide wire is formed at least partially of a superelastic metal alloy. In further aspects, the ultrasound transmission guide wire is formed at least partially of a shape memory alloy that exhibits superelastic properties when in its martensitic state, and further, the ultrasound transmission guide wire is formed of a nickel-titanium alloy.
In further features, an ultrasound transmission guide wire for use in an ultrasonic angioplasty device is provided, the ultrasound transmission guide wire having an elongated shaft, a proximal end configured to be connected to an ultrasound transducer, and a distal end for applying ultrasonic energy to an area of vascular lesion, the ultrasound transmission guide wire comprising a core including, in atomic percent, from about 28 to about 52 percent nickel, from about 48 to about 52 percent titanium, and up to about 20 percent of at least one alloying element selected from the group consisting of palladium, chromium, and hafnium. In more detailed aspects, the alloying element is hafnium or palladium, and is present, in atomic percent, in a range from about 3 to about 20 percent.
In another more detailed aspect, the alloying element is present, in atomic percent, in a range from about 5 to about 11 percent.
In another aspect, the alloying element is palladium. In yet another aspect, the alloying element is chromium and is present, in atomic percent, in a range up to about 3 percent. In more detail, the alloying element is present, in atomic percent, in a range from about 0.1 to about 1.0 percent, and in yet more detail, the alloying element is present, in atomic percent, in a range from about 0.2 to about 0.5 percent.
In another aspect, the ultrasound transmission guide wire comprises threads disposed at its proximal end, the threads configured to connect to a connecting device for an ultrasound transducer to thereby communicate ultrasonic energy to the elongated shaft and to the distal end of the ultrasound transmission guide wire.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example, the features of the invention.